Method and device for moulding a tripod spider

ABSTRACT

A method of and device for forming a tripode star for a tripode joint, which tripode star comprises an annular hub member and three arms which adjoin the hub member, extend radially relative to a longitudinal axis (A) and form faces of spherical portions each positioned circumferentially relative to arm axes (Z) of the arms, wherein, in a first production stage, the hub member and the three arms are preformed from a blank by means of a first tool divided in a plane (E 1 ) containing the arm axes (Z) and wherein, in a second production stage, pairs of burr-free faces of spherical portions positioned opposite one another in the circumferential direction relative to the hub member ( 12 ) are formed on to the preformed arms by means of a second tool divided in planes extending through the longitudinal axis (A) of the hub member and through the arm axes (Z).

BACKGROUND OF THE INVENTION

The invention relates to a method of and device for forming a tripodestar for a tripode joint, which tripode star comprises an annular hubmember and three arms which adjoin the hub member, extend radiallyrelative to the longitudinal axis of the hub member and which each formfaces of spherical portions positioned circumferentially relative to thearm axes of the arms. Tripode stars of said type are used in tripodejoints wherein roller carriers for the rollers are arranged on thetripode arms, which roller carriers are each provided with axial boresengaged by the tripode arms in a substantially play-free way. In thisway, the roller carriers are axially displaceable and swingingly movablerelative to the tripode arm. In this way, it is ensured that, when anouter joint part and an inner joint part of a tripode joint rotate withone another in an angular position relative to one another, the tripoderollers supported on the roller carriers can be guided, so as to carryout a pure rolling contact movement in the tracks of the outer jointpart, with the axes of the tripode rollers always being parallelrelative to themselves.

Tripode stars/inner joint parts of the above-mentioned type have so farbeen produced by using a cylindrical blank for forming the hub memberand the three arms by forward extrusion by means of a tool divided inthe plane containing the arm axes, as a result of which there occurs aburr extending in the central plane of the tripode star. During asubsequent production stage, which is not essential in this connection,first, the hub member is provided with a bore. This operation isfollowed by machining processes removing the burr which emerged duringthe deformation of the blank at least in the region of the faces of thespherical portions at the arms, which faces have to comprise a goodsurface quality as functional faces, which cooperate with the axialbores of the roller carriers. Said machining processes can take place inthe form of hard-turning or grinding carried out at the already hardenedtripode star.

SUMMARY OF THE INVENTION

It is the object of the present invention to simplify the forming methodused for the tripode stars of tripode joints of said type.

The objective is achieved in that, first, as before, in a firstproduction stage, the hub member and the three arms are pre-formed froma blank by means of a tool divided in the plane containing the arm axesand that, in a second production stage, pairs of burr-free faces ofspherical portions positioned opposite one another in thecircumferential direction relative to the hub member are formed on tothe pre-formed arms by means of a tool divided in planes extendingthrough the longitudinal axis and through the arm axes. During thesecond production stage, the burr which emerged during the firstproduction stage is removed, and there are produced finished functionalfaces which do not need any subsequent machining and whose surfaceroughness is clearly reduced. It is appreciated that, during the firstproduction stage, the faces of the spherical portions at the arms haveto be pre-formed as far as possible, but still comprising the materialallowance required for the second production stage.

It is possible, for the centers of the provisional faces of thespherical portions, after the first production stage, still to bepositioned at a certain distance from the longitudinal axis and toassume their final position on a so-called pitch circle diameter onlyduring the second production stage.

According to a particularly preferable embodiment, it is proposed that,in the course of the first production stage, the arms are formed so asto comprise flattened portions arranged opposite one another in thedirection of the longitudinal axis of the hub member. In this way itbecomes possible, during the second production stage, for the arms togrow in this region, without their design-related functions beingadversely affected, i.e. the remaining flattened portions are stillpositioned inside the spherical contour complementing faces of thespherical portions and thus within the bore diameter of the rollercarrier. Analogously, the same applies to the arm heads radially growinginto an outer free space in the tools for the purpose of carrying outthe second production stage.

According to a first embodiment of the inventive method, the tripodestar, during the second production stage, can be held radiallyfloatingly relative to the second tool in that clamping tongs forexample hold the hub member in an accurate axial alignment only.

According to a second embodiment of the inventive method, the tripodestar, during the second production stage, can be held so as to be firmlysupported relative to the second tool, for example in a third tool whichis divided in a plane containing the arm axes.

The forming process carried out on the arms in the second productionstage can take place in three individual operations or in one singleforming operation.

In any case, an inventive tool for carrying out the second productionstage is characterised by at least one set of tools including of twosymmetric mold halves for forming a tripode arm, which tool set isdivided in a plane extending through the longitudinal axis and throughan arm axis. These characteristics apply regardless of whether thesecond production stage is carried out for each arm individually or forall three arms simultaneously. In a preferred embodiment, the at leastone tool set is open at the arm end faces positioned opposite oneanother in the direction of the longitudinal axis.

In one embodiment of the tool for carrying out the second productionstage at one tripode arm only, the mold halves of the one single toolset are designed so as to be linearly guided and movable in oppositedirections perpendicularly relative to the dividing plane.

A further embodiment of the tool for simultaneously carrying out thesecond production stage on all three arms is characterised in that thetool comprises three circumferentially distributed tool sets with moldhalves with outer tool faces positioned approximately radially relativeto the longitudinal axes and with three wedge elements which arepositioned between the tool sets, which can be moved radially inwardlyand whose wedge faces cooperate with the outer tool faces of adjoiningtool sets. All mold halves can be designed so as to be movableindependently of one another and held in a cylindrical ring, or therecan be provided three first mold halves which are independent of oneanother and are held in a cylindrical ring, whereas three secondcomplementary mold halves are firmly connected to one another by a disc,or three first mold halves can be firmly connected to one another by afirst disc, with three second complementary mold halves being firmlyconnected to one another by a second disc.

A further embodiment of the tool for carrying out this production stageis characterised in that the tool comprises three circumferentiallydistributed tool sets with mold halves with outer tool faces which arearranged in pairs, which extend parallel to the arm axes and which arepositioned wedge-like relative to one another and with three wedgeelements which can be moved axially in the longitudinal direction, whichare positioned between the tool sets and which are supported in acylindrical ring and which, by means of their wedge faces, cooperatewith the outer tool faces of adjoining tool sets.

One tool, by means of which the arms can be machined only individuallyduring the second production stage, but which permits the completetripode star to be securely supported during this forming operation ischaracterised in that the mold halves are provided in the form of a pairof punches which are guided in transverse bores of a holding tool whichreceives the complete tripode star and which is divided in the planecontaining the arm axes.

BRIEF DESCRIPTION OF THE DRAWINGS

An inventive tripode star and tools for carrying out the inventivemethod are illustrated in the drawings described below.

FIG. 1 is a plan view in the direction of the longitudinal axis of atripode star after the two forming stages in accordance with theinvention have been carried out.

FIG. 2 shows an inventive tool for carrying out the second productionstage.

FIG. 3 shows an inventive tool in a second embodiment

a) in an axial view

b) in a section extending perpendicularly relative to an arm axis.

FIG. 4 shows an inventive tool in a third embodiment

a) in an axial view

b) in a section through the longitudinal axis.

FIG. 5 shows an inventive tool in a fourth embodiment

a) in an axial view

b) in a section extending perpendicularly relative to the arm axis

c) in a section through the longitudinal axis.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a tripode star 11 comprising an annular hub member 12 withan inner bore 13, and two of three circumferentially distributed arms14. The arms 14 comprise a neck 15 with a smaller diameter. The arm head14 is shown to comprise flattened portions 16, 17 positioned oppositeone another in the axial direction of the hub member, as well as faces18, 19 of spherical portions positioned opposite one another in thecircumferential direction of the hub member. The centers of said facesof the spherical portions are positioned on the arm axes Z and determinethe so-called pitch circle R. All contours are shown in continuous linesafter the second production stage has been carried out, whereas dashedlines indicate the contours existing after the first production stage.The Figure makes it clear that the hub member 12 and the arm necks 15are finished-formed even after the first production stage, whereas thearms 14 themselves are still formed during the second production stagein respect of all their details, in particular as regards the positionof the centers relative to the longitudinal axis A. The first productionstage is carried out by a first tool (not shown) divided in the planeextending through the three arm axes Z, whereas the second tools for thesecond production stage are illustrated in the subsequent drawings.

FIG. 2 shows a tool with a tool set 21, 22 for forming an individual armin a second production stage, which tool is divided in a plane E2extending through the longitudinal axis A and an arm axis Z and of whichthe upper mold half 21 is connected to an upper punch 23 and the lowermold half 22 to a lower punch 24. In the direction of the axis A, thetool set 21, 22 leaves openings extending in opposite directions, sothat, while the faces 18, 19 of the spherical portions are being formed,material is able to flow towards the end faces 16, 17 of the individualarms 14, which end faces 16, 17 are positioned opposite one another inthe longitudinal direction. The tool illustrated here is suitable forforming only one arm at a time, so that the second production stage hasto be carried out for each arm individually, one after the other.

FIG. 3 shows a tool with three uniformly circumferentially distributedtool sets each comprising of two mold halves 31, 32 positioned on atable 40. The three first mold halves are firmly connected to oneanother by an upper disc and the three complementary mold halves arefirmly connected to one another by a lower disc 34. Alternatively, threeof the mold halves could be firmly connected to the table 33 or a disc,with only the complementary three mold halves being individuallyfloatingly arranged while being held in a cylindrical ring. However, itwould also be possible for all mould halves to be inserted into acylindrical ring so as to be freely adjustable in the circumferentialdirection. The angle α indicates the possible opening angle between themold halves after the wedge tools 39 have been withdrawn. The moldhalves comprise tool reverse sides 35, 36 which are positionedapproximately radially relative to the axis A and which cooperate withwedge faces 37, 38 of wedge tools 39 which are arranged between each twotool sets 31, 32 and which can be fed in radially. It can be seen quiteclearly that at the respective end faces 16, 17 of the arms 14, the toolsets produce recesses 41, 42, with material flowing into same during thesubsequent forming of the faces 18, 19 of the spherical portions.However, the material has to remain within the sphere complementing thefaces 18, 19 of the spherical portions. F refers to the force applied tothe wedge tools 39. All the remaining details have been given the samereference numbers as used in the previous Figures. Reference istherefore made to the respective description.

FIG. 4 shows a tool with three uniformly circumferentially distributedtool sets 41, 42 whose mold halves comprise tool reverse sides 43, 44which are arranged wedge-like relative to one another and are positionedparallel to the arm axes Z. The mold halves 41, 42 are supported on atable 45. The wedge reverse sides 43, 44 of two adjoining tool setscooperate with three wedge elements 49 which comprise wedge faces 47, 48inclined in opposite directions and which, in turn, are held in acylindrical ring 46 with a base plate 50, which cylindrical ring 46 canbe fed against the table 45 by force F. All the remaining details havebeen given the same reference numbers as used in the previous Figures.Reference is therefore made to the respective description.

FIG. 5 shows a tool with one single tool set 51, 52 whose mold halvesare provided in the form of punches which are guided in the receivinghalves 61, 62 of a holding tool which, in turn, is divided in a plane E1contained in a plane extending through the arm axis Z. In respect of itsmold cavity and division, said holding tool substantially corresponds toa first tool (not shown in this Figure) for carrying out the firstproduction stage. The mold halves 51, 52 which are divided in the planeE2 are moved towards each other by forces F to be able to carry out thesecond production stage. At the same time, the receiving halves 61, 62are held together by forces F_(h) for the purpose of fixing the tripodestar. All further details have been given the same reference numbers asused in the previous Figures. Reference is therefore made to therespective description.

What is claimed is:
 1. A method of forming a tripode star for a tripodejoint, said tripode star comprising an annular hub.
 2. A methodaccording to claim 1 wherein pre-forming the hub member and the threearms includes forming the arms so as to comprise flattened portionsarranged opposite one another in the direction of the longitudinal axis(A) of the hub member.
 3. A method according to claim 1 wherein formingpairs of burr-free faces includes holding the tripode star so as to beradially floating relative to the second tool.
 4. A method according toclaim 2 wherein forming pairs of burr-free faces includes holding thetripode star so as to be radially floating relative to the second tool.5. A method according to claim 1 wherein forming pairs of burr-freefaces includes firmly supporting the tripode star relative to the secondtool.
 6. A method according to claim 2 wherein forming pairs ofburr-free faces includes firmly supporting the tripode star relative tothe second tool.
 7. A forming tool for producing a tripode star for atripode joint, said tripode star comprising an annular hub member andthree arms which adjoin the hub member and extend radially relative to alongitudinal axis (A) of the hub member, and wherein each arm includespairs of burr-free faces of spherical portions positioned opposite oneanother in a circumferential direction relative to the hub member andpositioned circumferentially relative to an arm axis (Z) of therespective arm, the tool comprising: at least one tool set comprisingtwo symmetric mold halves for forming a tripode arm, said tool set beingdivided in a plane (E2) extending through the longitudinal axis (A) andthe respective arm axis (Z).
 8. A forming tool according to claim 7wherein each arm includes flattened portions positioned opposite oneanother in the direction of the longitudinal axis (A) wherein the at theat least one tool set is open at the flattened portions of therespective tripode arm. three wedge elements positioned between the toolsets and supported by a cylindrical ring, said wedge elements beingadapted to be fed axially in the longitudinal direction, and eachincluding wedge faces which cooperate with the outer tool faces ofadjoining tool sets.
 9. A forming tool according to claim 7 wherein themold halves are linearly guidable and movable in opposite directions,perpendicular relative to the plane (E2).
 10. A forming tool accordingto claim 8 wherein the mold halves are linearly guidable and movable inopposite directions, perpendicular relative to the plane (E2).
 11. Aforming tool according to claim 7 comprising: three tool setscircumferentially distributed around the longitudinal axis (A) and eachcomprising two mold halves having outer tool faces positionedapproximately radially relative to the longitudinal axis (A), whereinall of said mold halves are supported in a cylindrical ring; and threewedge elements positioned between the tool sets, said wedge elementsbeing adapted to be fed radially inwardly and each including wedge faceswhich cooperate with the outer tool faces of adjoining tool sets.
 12. Aforming tool according to claim 8 comprising: three tool setscircumferentially distributed around the longitudinal axis (A) and eachcomprising two mold halves having outer tool faces positionedapproximately radially relative to the longitudinal axis (A), whereinall of said mold halves are supported in a cylindrical ring; and threewedge elements positioned between the tool sets, said wedge elementsbeing adapted to be fed radially inwardly and each including wedge faceswhich cooperate with the outer tool faces of adjoining tool sets.
 13. Aforming tool according to claim 7 comprising: three tool setscircumferentially distributed around the longitudinal axis (A) and eachcomprising two mold halves having outer tool faces positionedapproximately radially relative to the longitudinal axis (A), whereinthree of said mold halves are supported in a cylindrical ring and threeof said mold halves are connected to one another by a disc; and threewedge elements positioned between the tool sets, said wedge elementsbeing adapted to be fed radially inwardly and each including wedge faceswhich cooperate with the outer tool faces of adjoining tool sets.
 14. Aforming tool according to claim 8 comprising: three tool setscircumferentially distributed around the longitudinal axis (A) and eachcomprising two mold halves having outer tool faces positionedapproximately radially relative to the longitudinal axis (A), whereinthree of said mold halves are supported in a cylindrical ring and threeof said mold halves are connected to one another by a disc; and threewedge elements positioned between the tool sets, said wedge elementsbeing adapted to be fed radially inwardly and each including wedge faceswhich cooperate with the outer tool faces of adjoining tool sets.
 15. Aforming tool according to claim 7 comprising: three tool setscircumferentially distributed around the longitudinal axis (A) and eachcomprising two mold halves having outer tool faces positionedapproximately radially relative to the longitudinal axis (A), whereinthree of said mold halves are connected to one another by a first disc,and three complementary mold halves are connected to one another by asecond disc; and three wedge elements positioned between the tool sets,said wedge elements being adapted to be fed radially inwardly and eachincluding wedge faces which cooperate with the outer tool faces ofadjoining tool sets.
 16. A forming tool according to claim 8 comprising:three tool sets circumferentially distributed around the longitudinalaxis (A) and each comprising two mold halves having outer tool facespositioned approximately radially relative to the longitudinal axis (A),wherein three of said mold halves are connected to one another by afirst disc, and three complementary mold halves are connected to oneanother by a second disc; and three wedge elements positioned betweenthe tool sets, said wedge elements being adapted to be fed radiallyinwardly and each including wedge faces which cooperate with the outertool faces of adjoining tool sets.
 17. A forming tool according to claim7 comprising: three tool sets circumferentially distributed around thelongitudinal axis (A) and each comprising two mold halves having outertool faces positioned, in pairs, in parallel to respective arm axis andarranged wedge-like relative to one another; and three wedge elementspositioned between the tool sets and supported by a cylindrical ring,said wedge elements being adapted to be fed axially in the longitudinaldirection, and each including wedge faces which cooperate with the outertool faces of adjoining tool sets.
 18. A forming tool according to claim8 comprising: three tool sets circumferentially distributed around thelongitudinal axis (A) and each comprising two mold halves having outertool faces positioned, in pairs, in parallel to respective arm axis andarranged wedge-like relative to one another; and member and three armswhich adjoin the hub member and extend radially relative to alongitudinal axis (A) of the hub member, and wherein each arm includesfaces of spherical portions each positioned circumferentially relativeto an arm axis (Z) of the respective arm, the method comprising: first,pre-forming the hub member and the three arms from a blank with a firsttool divided in a plane (E1) containing the arm axes (Z); and second,forming pairs of burr-free faces of spherical portions positionedopposite one another in a circumferential direction relative to the hubmember on to the preformed arms with a second tool divided in planes(E2) extending through the longitudinal axis (A) of the hub member andthrough the arm axes (Z).
 19. A forming tool according to claim 9wherein the mold halves comprise a pair of punches which are guided intransverse bores of a holding tool which accommodates the entire tripodestar and which is divided in a plane (E1) containing the arm axes (Z).20. A forming tool according to claim 10 wherein the mold halvescomprise a pair of punches which are guided in transverse bores of aholding tool which accommodates the entire tripode star and which isdivided in a plane (E1) containing the arm axes (Z).